Flash Flood Prediction Program

Time: 752 AM Thu July 20, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT Message 1’s have been issued for the entire District effective until Cooler and cloudy to start the day as a disturbance is poised to move over the District throughout the day today, through the evening with a slight chance for some overnight showers/isolated thunderstorms. Currently temperatures are in the low 60’s with highs expected in the upper 70’s to around 80 this afternoon. Dew points are currently elevated, in the mid to upper 50’s and will likely remain as the day progresses resulting in a good chance for isolated heavy rainfall today. Showers and thunderstorms have already initiated over portions of the District and will likely continue through the afternoon and evening. The best chance for storm activity within the District will be from NOW through midnight, with a few lingering showers through the overnight, tapering off between 2-4am. Multiple rounds of showers/thunderstorms will be possible this morning, afternoon and evening. Storm motions will be the typical W to E motions between 15-25mph which should help limit point rainfall amounts with some erratic storm movement possible off outflow boundaries. Storms may also contain large hail, strong winds, frequent cloud-to-ground lightning and possible an isolated land spout/weak tornado, mainly for eastern portions of the District, especially if temperatures increase into the 80’s. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers and thunderstorms will produce a 0.10-0.50” total, in 10-30 minutes. A moderate to strong thunderstorm will produce 0.50-1.00” total, in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm anchors off an outflow boundary, or training of thunderstorms could potentially produce up to 2.0” total in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1159 PM Current TO 1100 PM Jefferson County 1 Current TO 1159 PM Current TO 1100 PM Broomfield County 1 Current TO 1159 PM Current TO 1100 PM Douglas County 1 Current TO 1159 PM Current TO 1100 PM Adams County 1 Current TO 1159 PM Current TO 1100 PM Denver County 1 Current TO 1159 PM Current TO 1100 PM DIA 1 Current TO 1159 PM Current TO 1100 PM Arapahoe County 1 Current TO 1159 PM Current TO 1100 PM the City of Aurora 1 Current TO 1159 PM Current TO 1100 PM Arvada 1 Current TO 1159 PM Current TO 1100 PM Wheat Ridge 1 Current TO 1159 PM Current TO 1100 PM Lakewood 1 Current TO 1159 PM Current TO 1100 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Arapahoe Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Boulder Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Broomfield Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Denver Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Douglas Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Jefferson Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Foothills above 6500ft       Boulder Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Douglas Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED Jefferson Current TO 1159 PM THU 0.1" (90%) to 0.5" (70%) to 1" (35%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]